Switch to English Language Passer en langue franÁaise Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,327   Posts: 1,537,012   Online: 1136
      
Page 27 of 58 FirstFirst ... 172122232425262728293031323337 ... LastLast
Results 261 to 270 of 576
  1. #261
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Use either 2001 or 2010, and AFAIK they can be purchased. Some companies such as the Formulary will special order for you.

    PE

  2. #262

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    Speaking of approach, here's my general suggestion:

    1. identify what is important (not just useful)
    2. determine if it's worth tackling
    3. define your goal based on 1 and 2
    4. identify challenges (loosely separate from trivial things that require little work to achieve)
    5. do research, consult literature and experts, anything it takes to gather relevant information/data to deal with #4
    6. consider all possible alternate options and narrow down to the best
    7. test, test, test
    8. scrap it and start over, unless the result is up to expectation of #3.

    Do not add things without knowing what the objective is.
    Do not change things without knowing what the objective is.
    Do not use things without confirming they are effective and robust.

    If you donít identify a problem, you will not solve anything.
    If you donít define an objective, you will not achieve anything.
    If you donít identify whatís important, your work wonít be important.
    If you donít determine whatís worthwhile, your work wonít be worth much.

    Creativity plays role in steps 1 through 6. You have to be critical of your work in steps 7 and 8. Otherwise, you are only fooling yourself.

  3. #263

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    654
    Quote Originally Posted by Photo Engineer View Post
    Use either 2001 or 2010, and AFAIK they can be purchased. Some companies such as the Formulary will special order for you.
    PE
    Checking dequest.com, there is no 2001. Did you mean 2000?
    Anyway, it's handy that these are available as organic acids. Do you suppose they'll dissolve in PG and/or TEA?
    And I see a couple of other Dequest products that don't say they're acidic, such as the 2040 series. Do you recommend those?


    An interesting observation:

    Only a small amount of ascorbic acid dissolves into 40C PG with much stirring, even after hours of sitting.
    But if I add enough sodium metaborate to convert all that AA into sodium ascorbate, it all dissolves in about 1/2 hour with constant stirring.
    I attribute this to a difference in solubility limits in PG. I was dissolving 3.6g of AA into 16 ml of PG, and it failed until the metaborate was added.
    But this could make TEA problematic because it contains no sodium, and therefore can't create sodium ascorbate. I'll just have to try it...

    Mark Overton

  4. #264

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    654
    Quote Originally Posted by Rudeofus View Post
    Thanks, Mark, for your great efforts! Based on your thread here I have just ordered a bunch of raw chems and will be ready to try out some stuff in the near future.
    Wow! Nice to know that I'm not the only one learning. I find all this very interesting. Once you get your chems, you might try this concentrate:


    Propylene glycol .............. 19 ml
    Sodium metaborate .......... 2.5 g (2.05g needed to convert ascorbic, giving pH=8.0. rest boosts pH to 8.1)
    Ascorbic acid .................. 5.5 g
    Phenidone ...................... 0.08 g (adjusted to give 1.5x dev-time)
    Propylene glycol to .......... 25 ml (should need to add only 1 ml)

    Target pH is 8.1. Dilute 1+39 (i.e., 25 ml makes a liter). Add 60 g/L sodium sulfite to water separately first, and then add the concentrate. Add 50% to XTOL's times.

    My goal with this test-concentrate was to get XTOL's quality, but using 2/3's of its sulfite and 3/2's of its dev-time, so the sulfite would have about the same solvent-effect. Tests look good, so you might enjoy experimenting with this. I'm tired of pouring so much sulfite into developers, so I decided to try this sulfite-saver idea. You just might be able to dissolve the powders into 15 ml of PG, giving a total of 20 ml and a 1+49 dilution.

    Mark Overton
    Last edited by albada; 01-12-2012 at 11:38 PM. Click to view previous post history.

  5. #265
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Unless the properties of Dequest have changed, they should sissolve in either PG or TEA depending on polarity.

    But, they are not the only sequestrants usable here.

    PE

  6. #266

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    Quote Originally Posted by albada View Post
    My goal with this test-concentrate was to get XTOL's quality, but using 2/3's of its sulfite and 3/2's of its dev-time, so the sulfite would have about the same solvent-effect.
    If such thing can be done with no negative effects, why do you think Kodak engineers didnít do it?

  7. #267

    Join Date
    Jul 2010
    Location
    Southern USA
    Shooter
    Multi Format
    Posts
    3,785
    Quote Originally Posted by albada View Post
    Will do, and thanks for the heads-up.

    Another chemistry question: What would be a good acid to mix into TEA to adjust pH and provide decent buffering?

    I'm thinking of using only TEA (and no PG) as the carrier for the concentrate, about 22 ml of it per liter of developer. That'll push the pH too high even with the ascorbic acid in it, so another stronger acid is needed to pull it down. I'm hoping that 22 ml of TEA plus an acid to convert some TEA into its conjugate acid (pKa=7.8) will provide sufficient buffering to hold the pH at 8.2 or so. The question is: which acid?

    Thanks,

    Mark Overton
    You can vary the pH of the resulting working solution by using a mixture of TEA and PG for the concentrate. If 't' is the percentage of TEA in the concentrate then (1-t) is the percentage of PG. Using more TEA will results in a higher pH while using less will give a lower pH. Since the developer is a one shot it doesn't need to be buffered. On a thread several years ago I mentioned that I used a mix of equal parts TEA and PG with good results.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  8. #268

    Join Date
    Jan 2005
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    1,416
    Quote Originally Posted by Gerald C Koch View Post
    Since the developer is a one shot it doesn't need to be buffered.
    Not a good idea. If you have poor buffering system, your operating pH is extremely susceptible to small errors like the amount of ingredients or the pH of the water supplies.

  9. #269

    Join Date
    Apr 2008
    Location
    Escondido, California, USA
    Shooter
    35mm RF
    Posts
    654
    Quote Originally Posted by Photo Engineer View Post
    Unless the properties of Dequest have changed, they should sissolve in either PG or TEA depending on polarity.
    But, they are not the only sequestrants usable here.
    Good to know, and I've entered this into my chem-notes. Thanks.

    Quote Originally Posted by Ryuji View Post
    If such thing can be done with no negative effects, why do you think Kodak engineers didnít do it?
    Because the 50% boost in dev-time was too negative of an effect?
    I also have an untested version of this formula that uses half the sulfite and doubles the dev-time, but that means 7 min for Tri-X becomes 14 min, which will test folk's patience.

    Quote Originally Posted by Gerald C Koch View Post
    You can vary the pH of the resulting working solution by using a mixture of TEA and PG for the concentrate. If 't' is the percentage of TEA in the concentrate then (1-t) is the percentage of PG. Using more TEA will results in a higher pH while using less will give a lower pH. Since the developer is a one shot it doesn't need to be buffered. On a thread several years ago I mentioned that I used a mix of equal parts TEA and PG with good results.
    I few postings ago (here: http://www.apug.org/forums/viewpost.php?p=1279399), I tried using 5 g/L TEA as the alkali, and got very thin neg's with normal dev-times. The explanation of this failure was poor buffering. That experience made me a buffering fanatic. Well, I was thinking that the best chance at adequate buffering was to use as much TEA as possible, and counter the excess pH with some acid, such as Dequest that PE recommends. And maximum TEA means using it as the sole carrier in a concentrate, as PC-TEA does, which got me going along that line of thinking, which may lead nowhere. Anyway, can you post that equal-part formula? I'd be interested in seeing a successful formula.

    Mark Overton

  10. #270
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,619
    Images
    10
    Quote Originally Posted by Ryuji View Post
    If such thing can be done with no negative effects, why do you think Kodak engineers didnít do it?
    Ryuji & PE: Again, you play in a different league. Kodak engineers had to make all the films out there work, had to care about reasonable dev times, people abusing the dev and then bitching about poor results, people finding tiny deviations with expensive densitometers, shipping and storage, cost of raw materials and other things that neither Mark nor I care about.

    While I don't follow the Lomo approach in my photography, I will try to pursue a similar approach when it comes to mixing chems. You never know, I may turn into some sort of photo chemist in ten years and if not I at least had fun trying. I will stay away from chems which are dangerous (I won't get those legally anyway) and those which have to be special ordered from overseas in large minimum order quantities.

    My personal goal is to learn lots about this topic and to eventually create developers which can't be just bought:
    • devs which create more speed and pushability than Microphen, even if this means large grain or poor acutance. I use a 6x7 format camera and enlarge Delta 3200 to 10x15, 13x18 and 18x24, what do I care about grain? Sure, using 135 format with its faster lenses would gain me 2 stops, but I really like the 6x7 view finder for night shots.
    • devs which let me fine tune the balance between grain and acutance in a wide range by adjusting the ratio of a few ingredients, optionally by adding varying amounts of chems to HC-110, my goto developer.
    • bend the characteristic curve so it better accommodates shots into direct sun.
    • ...
    Trying to be the best of whatever I am, even if what I am is no good.



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  ó   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin